In a typical inkjet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally include a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An inkjet recording element typically includes a support having on at least one surface thereof an ink-receiving or image-forming layer and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support. The ink-receiving layer is typically either a porous layer that imbibes the ink via capillary action or a polymer layer that swells to absorb the ink. Transparent swellable hydrophilic polymer layers do not scatter light and therefore afford optimal image density and gamut, but may take an undesirably long time to dry. Porous ink-receiving layers are usually composed of inorganic or organic particles bonded together by a binder. The inorganic particles used are typically expensive colloidal or fumed alumina or silica particles. During the inkjet printing process, ink droplets are rapidly absorbed into the coating through capillary action, and the image is dry-to-touch right after it comes out of the printer. Therefore, porous coatings allow a fast “drying” of the ink and produce a smear-resistant image; however, porous layers, by virtue of the large number of air-particle interfaces, scatter light that may result in lower densities of printed images.
Highly swellable hydrophilic layers can take an undesirably long time to dry, slowing printing speed. Porous layers speed the absorption of the ink vehicle, but often suffer from insufficient gloss and severe dye fade. Porous layers are also difficult to coat without cracking.
Japanese Kokai 07-137432 describes an inkjet paper having an ink-absorbing layer containing polyester resin particles with internal pores. However, there is a problem with this element in that the average particle size of the polyester resin is greater than 0.5 microns, and the element will have low surface gloss.
Furthermore, inkjet prints prepared by printing onto inkjet recording elements are subject to environmental degradation. They are especially vulnerable to damage resulting from contact with water and atmospheric gases such as ozone. Ozone can bleach inkjet dyes resulting in loss of density. Porous layers are particularly vulnerable to atmospheric gases in view of the open pores. The damage resulting from the post-imaging contact with water can take the form of water spots resulting from deglossing of the top coat, dye smearing due to unwanted dye diffusion, and even gross dissolution of the image recording layer. To overcome these deficiencies, inkjet prints are often laminated. However, lamination is expensive, requiring a separate roll of material.
Efforts have been made to avoid lamination and yet provide protected inkjet prints by providing an inkjet receiver having an uppermost fusible, porous layer. Such inkjet elements are known in the art. Fusing the upper layer after printing the image has the advantage of both providing a protective overcoat for water and stain resistance and reducing light scatter for improved image quality.
For example, U.S. Pat. Nos. 4,785,313 and 4,832,984 relate to an inkjet recording element comprising a support having thereon an upper fusible, porous ink-transporting layer and a lower swellable polymeric ink-retaining layer, wherein the ink-retaining layer is non-porous.
EP 858905A1 relates to an inkjet recording element having a fusible porous ink-transporting outermost layer, formed by heat sintering thermoplastic particles, and an underlying porous ink-retaining layer to absorb and retain the ink applied to the outermost layer to form an image. The underlying porous ink-retaining layer is constituted mainly of refractory pigments. After imaging, the outermost layer is made non-porous.
EP 1,188,573 A2 relates to an inkjet recording material comprising in order: a sheet-like paper substrate, at least one pigment layer coated thereon, and at least one sealing layer coated thereon. Also disclosed is an optional dye-trapping layer present between the pigment layer and the sealing layer.
U.S. Pat. No. 6,497,480 to Wexler discloses inkjet media comprising both a fusible ink-transporting layer and a fusible dye-trapping layer. A base layer under the fusible layers may be employed to absorb ink-carrier-liquid fluid.
It is desirable to provide a cost efficient inkjet recording element comprising porous polymeric particles that perform as an image receiving layer and that can then be fused after printing, thereby obtaining high-density, high quality, images. It is also desirable to provide an improved inkjet printed element having a fused protective layer to render images resistant to water and stain.
It is an objective of this invention to provide an inkjet recording element that is inexpensive yet high quality. It is yet another objective of this invention to provide an inkjet recording element that will provide improved ink uptake speed and allow for faster drying. A further objective of the invention is to provide an inkjet recording element having high surface gloss. Another objective of the invention is to provide an inkjet recording element having a receiving layer that when printed upon has an excellent image quality and stability.